The present invention relates to an inductance element and a semiconductor device which includes the inductance element therein, and particularly to a structure of an inductance element which reduces signal loss brought about therein.
Recently, with rapid miniaturization of portable communication devices such as a cellular phone, it has been being required to realize high frequency integrated circuits, such as an IC (Integrated Circuit) and an LSI (large-scale integration), which are used in these devices, by using a circuit provided on a silicon semiconductor substrate.
In addition to passive elements such as a transistor, a resistor, and a capacitor, an inductance element is required in the high frequency integrated circuit. Thus, in order to realize miniaturization of a device using the high frequency integrated circuit, all the foregoing passive elements including the inductance element need to be provided on the silicon semiconductor substrate. The inductance element for a silicon IC is typically provided on the silicon semiconductor substrate via an insulating film, and is made, for example, by providing a belt-shaped conductive film of aluminum (Al) in a spiral manner (in a vortex manner) or in a meandering manner.
A structure of a conventional inductance element is described as follows by reference to FIG. 8 and FIG. 9. FIG. 8 is a plan view which schematically shows a structure of an inductance element formation section in the conventional semiconductor device. Further, FIG. 9 is a cross sectional view in a line D-Dxe2x80x2 of the inductance formation section of the semiconductor device shown in FIG. 8. Note that, in FIG. 8, insulating films 5, 6, and 7 are not displayed, but patterns are given to respective components. That is, the same component has the same pattern in FIG. 8.
As shown in FIG. 9, the conventional inductance element has the following structure. The insulating films 5 and 6 are provided on a main surface of a semiconductor substrate 4, such as a silicon semiconductor substrate, in this order. A connection wire 3, connected to one terminal of an inductance section which is composed of a conductive film pattern 1 described later, is provided on the insulating film 6. The inductance section, which is composed of the conductive film pattern 1 provided in a spiral manner (in a vortex manner) as shown in FIG. 8, is provided on the insulating film 7 which covers the connection wire 3.
In the inductance section which is composed of the conductive film pattern 1 in a spiral manner, the one terminal (drawing terminal) is formed at a substantially central portion of the spiral. Further, the inductance section is connected to the connection wire 3 via a via-hole (not shown) at a position of the terminal, that is, at a substantially central portion of the spiral.
The connection wire 3 is externally drawn from the inductance section as a drawing wire for connecting to an external portion of the inductance element. The inductance element is, for example, provided in a semiconductor device, that is, provided on a semiconductor substrate of the semiconductor device internally or externally. For example, the foregoing semiconductor substrate 4 is used as the semiconductor substrate of the semiconductor device, so that the inductance element is electrically connected to an electrode pad (not shown) etc, provided on the main surface of the semiconductor substrate 4, which is electrically connected to a transistor (not shown) etc. making up an integrated circuit such as an LSI.
However, in the conventional inductance element having the foregoing structure, when a current is applied to the inductance section, an excess current occurs on a surface of the semiconductor substrate 4 due to electromagnetic induction of a current applied to the conductive film pattern 1 making up the inductance section. Therefore, a resistance component of the semiconductor substrate 4 causes a high frequency signal passing through the inductance section to be reflected and to be lost. It is known that this results in deterioration of the performance of the conventional inductance element entirely.
Generally, it is often that the inductance element is used at a high frequency band. However, the signal loss of the semiconductor substrate 4 occurs frequently particularly at a high frequency band. The performance of the inductance element is deteriorated by a parasitic component which occurs due to a shape etc. of the conductive film pattern 1 making up the inductance section.
Thus, in the semiconductor substrate 4 of the conventional inductance element, a signal loss at an area under the spiral conductive film pattern 1 is extremely large, so that the inductance element cannot be preferably used at a high frequency band.
Then, as an improving measure, Japanese Unexamined Patent Publication No. 181289/1994 (Tokukaihei 6-181289) (publication date: Jun. 28, 1994) discloses an inductance element having the following structure. A grounded metallic thin film is provided near the conductive film pattern 1 formed above the semiconductor substrate 4, so that characteristic impedance is adjusted. Thus, reflection and loss of a high frequency signal are reduced.
Concretely, in the inductance element recited in Japanese Unexamined Patent Publication No. 181289/1994, the influence upon the semiconductor substrate 4, which is exerted by electromagnetic induction of a current applied to the inductance section, is reduced by forming an inductance section on a grounded metallic thin film, so that a signal loss of the semiconductor substrate 4, that is, a characteristic loss is reduced.
By reference to FIG. 10 and FIG. 11, the inductance element of the semiconductor device, recited in Japanese Unexamined Patent Publication No. 181289/1994, is described as follows. FIG. 10 is a plan view showing a schematic structure of an inductance element formation section of the semiconductor device recited in Japanese Unexamined Patent Publication No. 181289/1994. Further, FIG. 11 is a cross sectional view in a line E-Exe2x80x2 of the semiconductor device shown in FIG. 10. Note that, in FIG. 10, for the sake of convenience in description, the insulating films 5, 6, and 7 shown in FIG. 11 are not displayed, and patterns are given to the respective components. That is, in FIG. 10, the same pattern is given to the same component. Further, in the following description, the same signs are given to components having the same functions as components shown in FIG. 8 and FIG. 9, and description thereof is omitted.
In the foregoing semiconductor device, the insulating film 5 is provided as a first insulating film on a main surface of the semiconductor substrate 4, and a metallic thin film 2, which is a grounding metallic film (grounding potential layer), is provided on the insulating film 5 so that substantially all the surface of the semiconductor substrate 4 except for marginal portions is covered. Further, in the semiconductor device, after the metallic thin film 2 is coated by the insulating film 6 which serves as a second insulating film, the connection wire 3 which serves as a drawing wire for external connection at the inductance section is provided on the insulating film 6. Further, in the semiconductor device, the insulating film 7 which serves as a third insulating film is provided so as to cover the connection wire 3, and the conductive film pattern 1 making up the inductance section is provided in a spiral manner (in a vortex manner) on the insulating film 7.
However, in the inductance element recited in Japanese Unexamined Patent Publication No. 181289/1994, the grounded metallic thin film 2 is provided on the insulating film 5 formed on the main surface of the semiconductor substrate 4, so that parasitic capacitance is formed at a portion where the conductive film pattern 1 or the connection wire 3 is lapped by the metallic thin film 2 in a laminating direction above the semiconductor substrate 4. That is, between the conductive film pattern 1 and the grounded metallic thin film 2, and between the connection wire 3 used as a drawing wire of the conductive film pattern 1 and the metallic thin film 2, the parasitic capacitance is formed. Thus, in the inductance element, compared with an inductance element shown in FIG. 8 and FIG. 9, a thickness between the conductive film pattern 1 or the connection wire 3 and a grounding surface (grounding potential layer) decreases by a thickness of the insulating film 5, which is equivalent to a distance between a surface of the semiconductor substrate 4 and an underside of the metallic thin film 2. Therefore, in the inductance element of the semiconductor device recited in Japanese Unexamined Patent Publication No. 181289/1994, the parasitic capacitance (parasitic component) increases by the thickness of the insulating film 5, and attenuation of a signal level occurs, in a case where the inductance element is used as an inductance element for high frequency.
Thus, in the inductance element recited in Japanese Unexamined Patent Publication No. 181289/1994, the parasitic capacitance, which occurs between the conductive film pattern 1 making up the inductance section and the metallic thin film 2, causes a characteristic of the inductance element, furthermore, a characteristic of the semiconductor device having the inductance element therein to deteriorate.
Thus, it is required to develop an inductance element in which the loss is reduced, that is, to develop a high performance inductance element which can restrict the signal loss brought about by a resistance component of the semiconductor substrate 4, and to develop a semiconductor device using the inductance element.
Considering the foregoing problems, the present invention is created. The object of the present invention is to provide an inductance element and a semiconductor device in which signal loss which occurs in a semiconductor substrate is restrained, and a parasitic capacitance is reduced compared with a conventional inductance element.
In order to achieve the foregoing object, the inductance element according to the present invention, includes an inductance section, provided above a semiconductor substrate via insulating films, which is composed of a first conductive film pattern setted to have a predetermined inductance value, wherein an impurity region, which has a grounding potential and a denser impurity than that of the semiconductor substrate, is provided on the semiconductor substrate so as to be positioned at least at an area under the first conductive film pattern.
According to the structure, the impurity region is provided on the semiconductor substrate so as to be positioned at least at the area under the first conductive film pattern, and the impurity region has the grounding potential and the denser impurity than that of the semiconductor substrate. Therefore, it is possible to provide the following high performance inductance element. In the inductance element, it is possible to reduce reflection and loss of a high frequency signal passing through the inductance section which result from electromagnetic induction of a current applied to the inductance section, so that it is possible to restrict decline of the Q value which indicates the performance of the inductance element with respect to frequency.
Further, according to the structure, it is possible to enlarge a film thickness (distance) between the inductance section and a grounding surface, that is, a layer or an area which is used as the grounding potential layer, so that it is possible to reduce the parasitic capacitance, compared with the inductance element of Japanese Unexamined Patent Publication No. 181289/1994 (Tokukaihei 6-181289) . Thus, it is possible to reduce attenuation of a signal level which is brought about by the parasitic capacitance.
In order to achieve the foregoing object, the semiconductor device according to the present invention includes the inductance element according to the present invention. It is preferable that the inductance element is provided in the semiconductor device.
According to the structure, the inductance element is, for example, provided in the semiconductor device, so that it is possible to reduce reflection and loss of a high frequency signal passing through the inductance section which result from electromagnetic induction of a current applied to the inductance section, so that it is possible to restrict decline of the Q value which indicates the performance of the inductance element with respect to frequency. Besides, the parasitic capacitance can be reduced, so that it is possible to provide a semiconductor device having a high quality inductance characteristic.
Further, according to the structure, in the semiconductor device, the inductance element is separated from a semiconductor substrate on which an integrated circuit making up the semiconductor device is provided, for example, the inductance element is separated from an integrated circuit formation section (element formation section) of the semiconductor substrate, so that it is possible to prevent other elements from being influenced by noise.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.